1. Field
The present general inventive concept relates to an objective lens of a digital photographing apparatus, an actuator for focusing the objective lens, and an endoscope including the objective lens.
2. Discussion of the Background
Endoscopy is widely used in medical examination, diagnosis, and treatment of patients with internal organ problems. Endoscopy allows patients to recover fast after a procedure, and also offers doctors great flexibility when conducting surgical or other procedures. Thus, endoscopy is generally used in various types of hospitals and clinics.
Endoscopy apparatuses have been gradually developed in recent years. For example, an imaging unit has been developed from a fiber optic image guide for using a digital sensor. An objective lens has been developed to meet the demands of modern image sensors. Although a lens structure of an objective lens of an endoscope may be simple, the size of an endoscope is limited.
Recently, new image quality standards for endoscopes have been introduced. The maximum effective image resolution option has increased from 0.3 megapixels (MP) to 1.3 MP or higher. High image quality is important for the medical staff to view the affected area clearly. Since a size of an imaging unit is limited, a sensor size has remained constant, and to provide a possibility of obtaining the mentioned resolution, a pixel size has been reduced. However, with smaller pixel sizes (high resolution), it is difficult to obtain a wide depth of field (DOF) due to diffraction limitations.
In addition, to perform focusing with an objective lens used in an endoscope, at least one lens is moved along an optical axis. However, this operation increases a size of a lens system, a driving mechanism for moving a lens is complicated, and a control system therefor is also complicated. Moreover, a focusing system as described above may be inconvenient to use due to a short DOF at a near distance.